The purpose of this study is to learn how well atazanavir (ATV) works in combination with ritonavir (RTV) or saquinavir (SQV) with tenofovir (TDF) and a nucleoside to reduce the viral load of treatment experienced subjects with human immunodeficiency virus (HIV). There is a comparison arm with lopinavir (LPV)/RTV and TDF and a nucleoside.

Pearson correlations of the Cmin (trough plasma concentration), IQ (the ratio of Cmin of ATV to HIV IC50), and Number of baseline PI Mutations with HIV RNA change from baseline at Week 24 were explored.

Pearson correlations of the Cmin (trough plasma concentration), IQ (the ratio of Cmin of ATV to HIV IC50), and Number of baseline PI Mutations with HIV RNA change from baseline at Week 48 were explored.

Pearson correlations of the Cmin (trough plasma concentration), IQ (the ratio of Cmin of ATV to HIV IC50), and Number of baseline PI Mutations with CD4 cell count change from baseline at Week 24 were explored.

Pearson correlations of the Cmin (trough plasma concentration), IQ (the ratio of Cmin of ATV to HIV IC50), and Number of baseline PI Mutations with CD4 cell count change from baseline at Week 48 were explored.

The QT interval is a measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle. The QT interval was corrected for heart rate using Fridericia's (QTcF) formula.

The PR interval is measured from the beginning of the P wave to the beginning of the QRS complex, and reflects the time the electrical impulse takes to travel from the sinus node through the atrioventricular (AV) node and entering the ventricles. The PR interval is therefore a good estimate of AV node function.

The MACS adherence questionnaire asks patients how many medication doses they missed during the previous day, 2 days, 3 days and 4 days. Drug-specific questions included adherence with dose and frequency. Adherence was defined as taking all doses and numbers of pills as prescribed for each medication. This strict adherence cut-off was based on the guidelines stating that anything less than excellent adherence may result in a virus breakthrough and development of resistance.

The EQ-5D is a 5-item questionnaire to assess health-related quality of life in 5 health dimensions (mobility, self-care, usual activity, pain/discomfort, anxiety/depression) are scored on a 3-level scale: no problems (1), some problems (2), extreme problems (3). Using a standard algorithm, responses are summarized into a single score, the EQ-5D Health Index Score (HIS), which ranges between 1 (representing perfect health) and 0 (representing the worst imaginable health state or death). The smallest coefficient of change is 0.03.

The EQ-5D has a Visual Analog Scale (VAS), which is a feeling thermometer-like scale with a range between 0 and 100. Patients are required to draw a line from a box on the VAS scale to an actual mark on the thermometer-like scale that corresponds with a number that reflects their self-assessed health status at the time they are completing the questionnaire. Higher VAS scores indicate better overall health. There is no minimum clinically important difference reported in the literature for VAS.

=>16 years of age (or minimum age as determined by local regulations or as legal requirements dictate);

History of prior virologic response to at least one HAART regimen, defined as a 1.0 log10 decline or a decline in viral load to <400 c/mL by Roche Amplicor or <500 c/mL by Chiron Quantiplex branched DNA (bDNA) assay

Both females of child bearing potential and males must utilize effective barrier contraception to reduce transmission of sexually transmitted disease, including human immunodeficiency virus (HIV). Other contraception in addition to barrier methods is permitted; interaction between atazanavir and oral contraceptives has not been studied.

Subjects must be able to provide written informed consent;

Subjects should be available for follow-up for a period of at least 48 weeks

Prior use (=>3 days) of atazanavir, TVF or LPV/RTV; if history of SQV, then must be phenotypically sensitive

the current failing antiretroviral regimen must have been administered for at least eight weeks at he initiation of screening and must not include both a PI and NNRTI

Presence of a newly diagnosed HIV-related opportunistic infection or any medical requiring acute therapy at the time of enrollment

Proven or suspected acute hepatitis in the 30 days prior to study entry. Subjects with chronic hepatitis are eligible provided that their liver function enzymes (ALT/AST) are <3 x ULN

Previous therapy with agents with significant systemic myelosuppressive, neurotoxic, pancreatoxic, hepatoxic or cytotoxic potential within 3 months of study start or the expected need for such therapy at the time of enrollment of therapy with methadone or ribavirin/interferons or treatment with neurotoxic drugs or drugs that affect Cytochrome P450 3A4 (CYP3A4).

Active alcohol or substance use sufficient, in the Investigator's opinion, to prevent adequate compliance with study therapy or to increase the risk of developing pancreatitis or chemical hepatitis

Intractable diarrhea (=> 6 loose stools/day for at least 7 days consecutive days) within 30 days prior to study entry

If choosing 2'-3' dideoxyinosine (ddI) or 2',3'-didehydro-3'-deoxythymidine (d4T) as the NRTI: History or signs and symptoms of bilateral peripheral neuropathy => Grade 2 at the time of screening

Inability to tolerate oral medications

Any other clinical conditions or prior therapy that, in the opinion of the Investigator, would make the subject unsuitable for study or unable to comply with the dosing requirements.

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For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT00035932